The seasonal abundance and foraging behaviour of honeyeaters and their potential role in the pollination of Banksia menziesii

Seasonal changes in the abundances of five species of honey-eaters were assessed in relation to the flowering phenology of Banksia menziesii in banksia woodland near Perth, Western Australia. The total number of honeyeaters was significantly correlated to the number of inflorescences ofB. menziesii. New Holland Honeyeaters. Brown Honeyeaters and Western Spinebills were present throughout the year, whereas the larger honeyeaters (Red and Little Wattlebirds) were observed when B. menziesii was flowering. The foraging behaviours of the Little Wattlebirds, New Holland Honeyeaters, Brown Honeyeaters and Western Spinebills were similar and all were likely to effect pollination of B. menziesii florets. Differences in their foraging position at an inflorescence, number and direction of foraging probes, and the time spent at an inflorescence were minimal. Western Spinebills used inflorescences lower in the tree crown than the other species. Movements to inflorescences on different plants were inversely related to honeyeater size. Smaller honeyeaters were frequently chased from inflorescences by the larger species, increasing the proportion of distant foraging movements made by the smaller species. Also these interrupted visits were of shorter duration than uninterrupted visits. Visitation by smaller species, especially the Brown Honeyeater, may result in more cross pollinations although the effect on the reproductive success of B, menziesii is unknown.     

Nectar utilization and pollination by Australian honeyeaters and insects visiting Calothamnus quadrifidus (Myrtaceae)

Nectar availability in Calothamnus quadrifidus flowers was studied at Wongamine Nature Reserve in late spring (November). Despite some overnight depletion by moths and other invertebrates, more nectar was present in flowers at dawn than at the preceding dusk. Significant nectar depletion occurred within a few hours after dawn, mainly due to foraging by two honeyeater species. Lichmera indistincta and Phylidonyris nigra. Thereafter, nectar availability was maintained at relatively low levels, principally because of foraging by honeyeaters and honey bees. Apis mellifera, that became active during the warmer part of the day. Although individual honeyeaters consumed more nectar than A. mellifera, honey bees were so abundant that their total impact was greater than that of either honeyeater species for much of the day. Transfer of C. quadrifidus pollen between flowers is necessary in order to achieve a high level of seed set, as the flowers appear to be protandrous. Honeyeaters appeared to be considerably more significant pollen vectors than A. mellifera.     

Use of heathland and adjoining forest by honeyeaters: Results of a radiotracking study

Abstract New Holland (Phylidonyris novaehollandiae) and White-cheeked (Phylidonyris nigra) Honeyeaters that are resident in heathland during February and March, when there is negligible nectar production in that habitat, are expected to forage for nectar at that time in the adjacent open forest habitat. As nectar production in the heathland increases from then to June, while that in the forest decreases, the proportion of time spent by these birds in the forest should decrease over the same period. Radiotracking revealed that during February the residents did, as expected, spend time feeding on nectar in the forest and more time was spent in the forest in February than in April or June. However, the residents spent time away from the heathland throughout the year and spent more time away in June than in April. The resident honeyeaters spent about 80% of their time on our heathland grid overall. Radiotracking also indicated that there was no sharp distinction in behaviour between residents and other birds because birds that had been resident in the past but were not considered to be so at the time (absent residents), birds that would later be considered resident (future residents) and some birds that were never resident, all spent about half their time on the grid. The area that included 90% of heathland locations, estimated by radiotracking, for P. novaehollandiae and P. nigra averaged 0.48 ha per bird.     

Interspecific competition in Australian honeyeaters—depletion of common resources

Many species of honeyeaters and other nectar-feeding birds occur in most habitats in South Australia. They frequently feed on nectar of the same species of plants. A succession of species of plants provide nectar for birds throughout the year. Nectar is most abundant in winter and early spring and least abundant in summer and autumn. There is more nectar per flower and more flowers in winter and spring. Nectar is often depleted by honeyeaters, and sometimes other visitors (silvereyes, lorikeets and insects) between December and May. It is at times reduced to a level at which it is uneconomical for some species to exploit. There are seasonal movements of honeyeaters into areas of abundant nectar and out of these areas when nectar becomes scarce. Breeding coincides with peak abundance of nectar. Diversity of honeyeaters is probably maintained by an interaction of two types of competition, exploitation and interference. The larger species use the richest sources of nectar and aggressively exclude the smaller species (interference) whereas the smaller species can use poorer sources of nectar because their energy requirements are less (exploitation).     

Effects of flower removal on abundance and behaviour of honeyeaters in heathland near Sydney

Removal of almost all honeyeater nectar sources from a 5.6 ha area during February to July had no apparent effect on honeyeater nesting or total abundance. Behaviour in the experimental area was also generally unaffected except for the extent of nectar-feeding which was significantly reduced for the most commonly observed species. The honeyeaters must have compensated for the nectar removal by flying to nearby productive areas to feed on nectar. Nectar-removal had no significant effect on the species composition of resident honeyeaters but did affect the species composition of all observed honeyeaters. Nectar removal resulted in a decrease in the abundance of the large and dominant Little Wattlebirds (Anthochaera chrysoptera) and an increase in the abundance of the other, smaller species.     

Partitioning of nectar sources in an Australian honeyeater community

Feeding by honeyeaters was found to maintain nectar at low levels at three sites studied on Kangaroo Island in May-June 1978. The productivity of nectar at a site and position in a dominance hierarchy appeared to determine which bird species used each site. Correa was the main nectar source in the poorest area and produced 0.05 kJ m^?2 per day. The small eastern spinebill was the most abundant honeyeater. The purple-gaped honeyeater also occurred but fed mostly on honeydew. The medium sized New Holland honeyeater was common and territorial in the second area, where Banksia marginata and B. ornata inflorescences and Adenanthos flowers produced 0.7 kJ m^?2 of nectar per day. Spinebills and crescent honeyeaters also visited flowers and were sometimes chased by New Holland honeyeaters. The richest site was a flowering Eucalyptus cosmophylla tree (5.1 kJ m^?2 of nectar per day). A red wattlebird, the largest honeyeater, held a territory in part of this tree and chased other honeyeaters from the territory. New Holland, crescent and purple-gaped honeyeaters fed on flowers in other parts of the tree. The spinebill was absent. We conclude that nectar was partitioned along a spectrum of rich to poor sources. Larger more aggressive species used and sometimes defended the richest sources while the smaller birds used the poorer sources.     

Honeyeater population changes in relation to food availability in the Jarrah forest of Western Australia

The numbers of honeyeaters present at particular sites in the Jarrah forest varied significantly from month to month, with peak abundance occurring between May and September. Numbers also varied from site to site, depending upon the major plant species present. Honeyeater abundance was not limited by arthropod availability, but in many instances was closely correlated with the availability of nectar, particularly that produced by Dryandra sessilis. Large honeyeaters, such as Anthochaera chrysoptera and Phylidonyris novaehollandiae, were generally most abundant at times and sites of greatest nectar production. Small honeyeaters, such as Acanthorhynchus superciliosis, were never abundant but were present for most of the year. The production of nectar between October and December was such that more honeyeaters could have been supported than were actually present. Low numbers at these times can be explained in terms of reduced foraging efficiency that would have resulted from more widely dispersed flowers, and the possible availability of more rewarding nectar resources at other sites.     

The exploitation of floral nectar in Eucalyptus incrassata by honeyeaters and honeybees

Summary During October and November, 1977, a study of nectar production and nectarivore foraging in Eucalyptus incrassata was conducted at Wyperfeld National Park in south-eastern Australia in order to evaluate the extent to which introduced honeybees (Apis mellifera) compete with native honeyeaters for floral nectar. Data on nectar production, nectar availability, ambient air temperature and the numbers of visiting honeyeaters and honeybees were collected. Most of the daily nectar production in E. incrassata occurs early in the morning when temperatures are too low for insects to forage. In addition, insects, particularly honeybees, are unable to exploit nectar in the youngest flowers because the stamens are clustered tightly around the style. As a result of these temporal and structural characteristics of the flowers, honeyeaters are able to harvest most of the nectar. Honeybees potentially have access to 35–47% of the average daily production of floral nectar in E. incrassata and actually harvest considerably less. These data show that E. incrassata flowers are adapted to restrict insect foragers despite their superficially unspecialized appearance. Eight forest and woodland eucalypts do not have a flower stage which excludes insects and the significance of this difference is discussed.     

The foraging behaviour of Australian honeyeaters: a review and some comparisons with hummingbirds

The foraging behaviour of Australian honeyeaters is reviewed in terms of diet, foraging selectivity, foraging flight mode, quality and quantity of nectar encountered per flower, flower densities encountered and effect of predation. At the same time comparisons are made between honeyeaters and hummingbirds. These two groups of birds are superficially similar. Both feed on nectar and insects. Both tend to have long curved bills and tongues adapted for removal of nectar from flowers. Both tend to feed at long, red flowers. However, on close inspection, honeyeaters and hummingbirds are quite dissimilar. For example, many honeyeaters include fruit in their diets. Hummingbirds almost never eat fruit. Honeyeaters appear to be considerably less nectarivorous and more insectivorous than hummingbirds. Honeyeaters are, for the most part, larger than hummingbirds and they usually perch while feeding whereas hummingbirds usually hover. Honeyeaters but not hummingbirds often flock while feeding. Predation appears to be considerably more important for honeyeaters than for hummingbirds. Territorial defense of flowers seems common in hummingbirds but uncommon in honeyeaters. These differences are discussed in detail and explanations are offered for them wherever possible.     

Consequences of differences in body mass,wing length and leg morphology for nectar-feeding birds

Nectar-feeding birds are prominent in many parts of the world, and vary with respect to body size. Despite the availability of considerable morphometric data, few concerted efforts have been made to assess the influence of attributes such as mass, wing length and leg morphology upon the speed, acceleration, mode and energetic cost of movement by birds between flowers when foraging for nectar. This review attempts to consolidate and interpret available data and highlight areas where further investigations appear warranted. Australian honeyeaters are generally larger, and American hummingbirds smaller, than Hawaiian honeycreepers and sunbirds of Africa or Asia. Sunbirds, honeyeaters and honeycreepers generally perch while extracting nectar from flowers. Hummingbirds usually hover, apparently because suitable perches close to flowers are lacking, and not because hovering increases the speed at which flowers can be visited. Honeyeaters move from one flower to another at speeds that are at least as great as those for hummingbirds. Most passerine nectarivores need to ingest more nectar per day than hummingbirds in order to maintain energy balance, some species devoting more than 60% of the day to foraging. The major consequence of reduced foraging activity by hummingbirds, which spend only 5–30% of the day in this manner, appears to be male emancipation from nest construction and care of offspring. Large nectarivores have a greater capacity to store surplus food and to fast than smaller birds, and so can take advantage of short-lived peaks in nectar abundance. Nectarivores such as honeyeaters should therefore be favoured by the rapid diurnal changes in nectar availability which are characteristic of many Australian and African habitats. Body mass also determines the likely access to rich sources of nectar through size-related interspecific dominance hierarchies. In all families, larger species tend to monopolize the most rewarding nectar supplies, forcing smaller subordinate species to use poorer, more scattered sources. Within particular species, males usually have longer wings and greater masses than females. These variations imply that the two sexes differ with regard to their foraging ecology, although few supporting data are currently available.     

Nectar depletion and its implications for honeyeaters in heathland near Sydney

Several researchers have attempted to calculate whether depression of nectar resources by Australian honeyeaters is likely to limit their densities. Such calculations can be misleading, however, and do not directly test whether birds depress nectar availability. I monitored changes in nectar availability during the 8–9 months that honeyeaters bred in heathland near Sydney, and caged inflorescences to test whether nectar availability was being depressed by birds. There were pronounced seasonal changes in nectar availability in each of 2 years, and caging substantially increased the amounts of nectar in inflorescences during months when nectar production was low. The effects of caging must have resulted from exclusion of honeyeaters, as: (i) open-ended cage controls showed that the effects of caging resulted from exclusion of foragers, not from artifacts of caging; (ii) day-only and night-only caging showed that nectar was depleted only during the day: and (iii) observations showed that cages did not exclude any diurnal foragers other than honeyeaters. Resident honeyeaters spent more time foraging during months when nectar was scarce, implying that the rates at which they could obtain nectar were affected by changes in nectar availability. It is therefore possible that the depletion of nectar by honeyeaters could have limited their densities. However. I argue that such limitation could only be inferred safely if nectar-supplementation experiments showed survival and/or reproduction to be limited by nectar availability.     

Mutualistic interdependence between mistletoes (Amyema quandang), and spiny-cheeked honeyeaters and mistletoebirds in an arid woodland

The mutualism involving mistletoes (Amyema quandangj, spiny-cheeked honeyeaters (Acan-thagenys rufogularis) and mistletoebirds (Dicaeum hirundinaceum) was studied in arid woodland in South Australia between 1980 and 1984. Plants and birds were locally interdependent: mistletoes supplied a continuous resource of fruits or nectar that sustained permanent populations of pollinators (honeyeaters) and dispersers (honeyeaters and mistletoebirds). The reproductive phenology of Amyema quandang was central to the interactions. Amyema quandang flowered in winter and annual fruit crops overlapped so that ripe fruit was continuously available. Spiny-cheeked honeyeaters obtained most of their energy requirements from mistletoe nectar in winter and mistletoe fruit in summer. Higher honeyeater densities were sustained by flowering in winter. Mistletoebirds were present in low density throughout the year and subsisted on a diet of mistletoe fruit and a few insects. The reproductive strategy of A. quandang probably evolved in response to the pollination and dispersal service provided by honeyeaters in inland Australia. Neither spiny-cheeked honeyeaters nor mistletoebirds have adaptations resulting from evolutionary interactions with A. quandang. The high specificity of their mutualism is a result of: (i) the abundance of A. quandang in relation to other nectar and fruit producing plants in the community: (ii) the year-round production by A. quandang of the primary source of fruit or nectar for honeyeaters and mistletoebirds: (iii) the facultative specialization of both birds on A. quandang; and (iv) the reluctance or inability of other frugivorous birds in the community to consume A. quandang fruit.     

The foraging of New Zealand honeyeaters

Abstract

New Zealand has three species of honeyeaters, all of which feed on nectar, fruit, and ‘insects’. There is disagreement between published data and those becoming available from long-term studies on the relative proportion of these items in the diet. The effect of factors such as body size, dominance status, degree of movement, and time of year on diet and foraging behaviour are outlined, and predictions of differences between species and between sexes are made. A brief comparison of foraging in relation to the flora is made between New Zealand and Australian species.     

Pollinator visits to floral colour phases of Fuchsia excorticata

Abstract

Fuchsia excorticata is a gynodioecious tree (endemic to New Zealand) which is pollinated by honeyeater birds. Red, tubular flowers are common among bird-pollinated plants, and the tubular flowers of F. excorticata change colour from green to red. The purpose of the present study was to describe the timing of the colour change, dropping of the floral tube, and nectar production of F. excorticata and to determine how bellbirds (Anthornis melanura) and two introduced species of nectar robbers (Zosterops lateralis and Bombus sp.) respond to the different colour phases.

Floral tubes fell off about 11 days after anthesis in both sexes, with colour change occurring on about Day-4 for female trees and on about Day-5 for hermaphrodite trees. Green-phase hermaphrodite flowers produced significantly more nectar/day than did green-phase female flowers, while red-phase flowers did not produce nectar in either sex. All three floral visitors studied preferentially visited green-phase flowers and virtually ignored the nectarless flowers in the red phase. These results contrast with the general association between red, bird-pollinated flowers and the presence of a nectar reward. We suggest that the non-migratory habit of the New Zealand honeyeaters and the lack of native insect visitors to this species may account for this anomalous green-to-red colour change.     

Honeyeater foraging: A test of optimal foraging theory

Honeyeaters (Meliphagidae) were observed foraging for nectar from Lambertia formosa inflorescences, each of which has seven flowers. The frequency distribution of numbers of flowers probed per visit to an inflorescence was found to be bimodal, with one peak at two and the other at seven. It is hypothesized that this frequency distribution results from a rule of departure from inflorescences that maximizes the net rate of energy gain. Patterns of nectar distribution were determined for a large sample of inflorescences. In addition the extent to which the honeyeaters re-probe flowers during a visit to an inflorescence was estimated. From these data and from field measurements of the times required by the honeyeaters to perform the various foraging behaviours, computer simulations of honeyeater foraging were constructed. These simulations led in turn to optimal frequency distributions of numbers of flowers probed per inflorescence that were bimodal but had peaks at 1 and 7 instead of 2 and 7. Although the observed and predicted behaviour were consequently similar, the difference between them was nevertheless significant. This difference could have been due to the birds' transient occupancy of the study area.     

Status and foraging in New Zealand honeyeaters

Abstract

Aggression is a common feature of sociality among nectar-feeding birds, and these have been used to consider many aspects of ecological theory, for example community structure, foraging patterns, social organisation and plant-pollinator systems.

Knowledge of aggression among and within New Zealand's honeyeater species is reviewed. Additional information on the importance of various asymmetric cues as learned predictors of status is considered. High-status individuals appear to gain access to nectar in all situations.

Honeyeaters are monogamous and the relationship between the sexes is examined. Even when mates are not formally associated, both appear to benefit from the presence of the other. Examples of the effect of status on pollination efficiency are also considered.

Workers are urged to consider status and individual differences if we are to increase our understanding of community structure, foraging and plant-pollinator interaction.     

Relationship between nectar production and seasonal patterns of density and nesting of resident honeyeaters in heathland near Sydney

Some individual honeyeaters were repeatedly seen near the same location over at least a 2 day period and were considered resident in the present study. Such resident honeyeaters (mostly New Holland and White-cheeked Honeyeaters) were present on the heathland study areas from about February until about October. Production of nectar energy is negligible prior to April and low after October. It is hypothesized that the density of residents is determined by their ability to obtain energy in nearby habitats while establishing nesting sites in the heathland in February and March. Nesting tended to occur between April and July when there was sufficient production of nectar-energy.     

Flowering phenology,seed set and bird pollination of five Western Australian Banksia species

Flowering phenology and seed set characteristics of five species of Banksia were studied in relation to the nectarivorous birds which feed at their inflorescences. Within the Banksia woodland at the study site near Perth, the flowering seasons of the Banksia species were sequential and only slightly overlapping, providing a year-round nectar source. Although honeyeaters visited alt five species, seed set was very low in each case. Caging experiments indicated that, in B. attenuata at least, alternative pollinators may play a more important role in pollination than do nectar-feeding birds. It is suggested that non-avian pollinators, predatory insects, and characteristics of the breeding system may also have been important in the evolution of the observed flowering phenology and patterns of seed set.     

Bills and tongues of nectar-feeding birds: A review of morphology,function and performance,with intercontinental comparisons

The bills and tongues of nectar-feeding birds differ from continent to continent. The major differences are that: (i) the tongues of A Australian honeyeaters are broader any more fimbricated at the tip than the bifurcated tongues of sunbirds and hummingbirds; (ii) the bills of hummingbirds are more uniformly narrow and taper less markedly towards their tips than those of sun-birds and honeyeaters; and (iii) bill curvatures are generally greater for sunbirds and honey-creepers than for hummingbirds. A variety of hummingbirds has straight or even slightly upturned bills, while bills for all sunbirds, honeycreepers and honeyeaters are decurved to some extent. Despite differences in tongue morphology, hummingbirds, sunbirds and honeyeaters extract nectar at a similar range of rates, averaging approximately 40 γL s^?1 from ad libitum feeders, and 1–15 γL^?1 from flowers. All tongues collect nectar by capillarity, with licking rates of 6–17 s^?1. Licking behaviour has been little studied, although speeds of licking respond to changes in sugar concentration and corolla length. The tongues of honeyeaters are broad, and may need to be brush-tipped in order to allow capillary collection of nectar. Brush-tipped tongues can cover large surface areas on each lick, and may allow honeyeaters to exploit nectar and honeydew that is thinly spread over large surface areas. Bill lengths of nectarivorous birds are similar in all regions, though species of hummingbird have the shortest and longest bills. Bill lengths largely determine the range of floral lengths that can be legitimately probed. Maximum floral lengths exceed bill lengths, since hummingbirds, sunbirds and honeyeaters protrude their tongues beyond the tips of their bills. Rates of nectar extraction, however, decline rapidly once the floral length exceeds bill length. Decurved bills may have evolved in honeyeaters and sunbirds to enable perching birds to reach flowers at the ends of branches more easily. Consistent differences in bill length between the sexes suggest that males and females may exploit different floral resources or different proportions of the same resources. For honeyeaters and sunbirds, males have longer bills than females, but the reverse is true for many hummingbirds.     

Movements of groups of tui (Prosthemadera novaeseelandiae) in winter and settlement of juvenile tui in summer

Abstract

An individually colour-banded population of tui (Meliphagidae) was studied and individuals were shown to move over sometimes large distances in search of nectar during most of the year. However, individuals were localised into small foraging areas when nectar was abundant during summer breeding.

Tui forage a regular route, taking their newly independent young with them through winter. These family groups sometimes consist of previous years' young and also other adults. These same group members nest near each other during summer and their offspring establish nesting areas nearby in following years.